Has anybody heard of this theorem? I remember vaugely that it has to do something with the work being done on magnetic dipoles / spins. I can't find it anywhere on the internet. I'm really curious...

Thanks!

This theorem states that a system of N charges (not dipoles) in a magnetic field has zero magnetic susceptivity. I have studied this subject for my Statistical mechanics exam, I had to show the validity of this theorem. It can be done by showing that the partition function of this system is independent on the magnetic field.